Cartridge for an ion density measuring instrument



FIG. 1 is a front elevational view of a cartridge for an ion density measuring instrument showing my new design;

FIG. 2 is a rear elevational view thereof;

FIG. 3 is a top plan view thereof;

FIG. 4 is a bottom plan view thereof;

FIG. 5 is a right side elevational view thereof; and,

FIG. 6 is a left side elevational view thereof; and

FIG. 7 is a top, left and front side perspective view thereof; and,

FIG. 8 is a bottom, right and front side perspective view thereof. 

The ornamental design for a cartridge for an ion density measuring instrument, as shown. 